A disk device, for example, a hard disk drive (HDD) comprises a plurality of magnetic disks disposed to be rotatable in a housing, and a plurality of magnetic heads which read/write data from/to the magnetic disks, and a head actuator which supports the magnetic heads to be movable with respect to the respective magnetic disks.
The head actuator includes an actuator block supported to be rotatable, and a plurality of head suspension assemblies (also referred to as head gimbal assemblies) each extending from the actuator block and supporting the respective magnetic head in its distal end portion. The head suspension assemblies each includes a base plate one end of which is fixed to an arm, a load beam extending from the base plate, a tab extending from a distal end of the load beam and a flexure (wiring member) provided on the load beam and the base plate. The flexure includes a displaceable gimbal portion, and a respective magnetic head is supported on the gimbal portion. The load beam includes a pivot and the respective magnetic head is located to be overlaid on the pivot.
Moreover, the disk device comprises a ramped loading mechanism which holds a magnetic head at an unloading position spaced from the respective magnetic disk when the magnetic head moves to the outermost circumference of the magnetic disk. Usually, the ramped loading mechanism includes a ramp provided in the housing and the tab of the respective head suspension assembly. As each tab runs onto a corresponding step of the ramp, the magnetic head is held at the unloading position.
In the disk device, for example, when the magnetic head is loaded on a magnetic disk and the height of the base plate varies, a leverage movement occurs on the dimple as the fulcrum, thereby varying the height of the distal end of the tab. Or when the tab is on the ramp, a leverage movement occurs on a contact point (ramped loading point) between the ramp and the tab as the fulcrum, and the height of the distal end of the tab varies. These variations in the height of the distal end of the tab are likely to cause such problems as failure of the head unloading operation and crash of tabs locating back to back with respect to each other. In order to ensure reliable head loading and unloading operations, the diameters of the entrance and exit of the ramp and the distances between the entrances and between the exits must be enlarged so as to cope with the variations in the height of the distal end of the tab, which may be an obstacle when designing to reduce the height of a ramp and increase the number of magnetic disks.